This customizable can link multiple PET bottles together. Measure your bottle size and subtract a little bit (0.5 mm is a goot start) to get a tight fit. Pressurizing the bottles then creates a very stiff and lightweight structure. This linking system is a versatile alternative to glue, tape and other methods.
In the post-printing section it is shown how PET bottles can be pneumatically linked together. Two methods are available: one with the M5 screw system (TIKI 4 x M5) and one with plain 4 mm tubes.
The cover photo also shows the Non-return valve, Shut-off valve, 5/3-way valve manifold and Parametric pneumatic cylinder.
Like in every pneumatics project, using air pressure in your custom creations is at your own risk. This especially applies to pressurizing PET bottles.
Multiple bottle linkers can be printed at once in a stack. The ideal gap size depends on your specific printer characteristics. I use a 0.2 mm gap on my Prusa i3's which allows the linkers to be separated easily. Slicer settings: maximize number of perimeters!
Instead of a 0.2 mm you could also specify a much larger gap and simply let the slicer take care of support everywhere.
A M5 x 4 mm socket (straight or T-piece) together with a M5 nut is very effective in creating a pneumatic connection on bottle caps. Drill a 5 mm hole and screw the parts together as pictured.
Some caps may be too thin and generate cracks under pressure originating from the drilled hole. So I use a cap reinforcer disc inside which provides some additional strength to the cap.
It is also possible to drill a 3.2 to 3.5 mm hole and guide the 4 mm tube through it. A diagonal-cut tip and pliers help in getting the tube through the small hole. If necessary, a leaky hole can be made airtight by applying some blue silicone on the tube.
This complete system also incorporates a non-return valve with bike pump nozzle, two shut-off valves, a pressure gauge, a manual 4/2-way valve manifold and a customizable pneumatic cylinder. With both valves shut off (red knobs vertical) the bottle pressure is preserved indefinitely. With valves opened the pressure very slowly decreases due to tiny leaks in the 3D printed parts.